Recently we have observed various types of DNS anomalies due not only to misconfigurations such as lame delegations, but also due to malicious DoS attacks on DNS servers. However, discussion of DNS anomalies are mainly focused on DNS root servers and authoritative servers, and DNS cache servers have been hidden inside providers and rarely exposed.

The authors report their experiences with high-load DNS cache servers with regard to worms and misconfigurations. Although providers are always preparing such high loads, everybody will be happy if unnecessary DNS queries are avoided. Firstly, the authors describe the heavy load caused by worms, and suggest how to avoid the problem. Secondly, the authors present the heavy load caused by an authoritative server which has oversize records. The authors propose modifying BIND as a workaround.

About the Presenters
Katsuyasu Toyama is a senior research engineer at NTT Laboratories. He was involved with the establishment of the first Japanese datacenter company, Internet Multifeed Co., in 1997, and there he designed JPNAP's network and services in 2000. Toyama-san's current interests focus on bridging network operations and network research, especially the core technologies of the Internet, such as interdomain routing, name resolution, and security.

Chika Yoshimura joined NTT Communications Corporation in 2003, immediately after she earned her baccalaureate degree from Keio University in Japan. Her work focuses on operations of the Domain Name System in OCN, which is an ISP in Japan.